1. Field of the Invention
Embodiments of the invention generally relate to removal of a deposited conductive layer along an edge of a substrate. More particularly, embodiments of the invention relate to an electrode configured to polish a substrate edge during electrochemical mechanical processing of a substrate face.
2. Description of the Related Art
In the fabrication of integrated circuits (IC) and other electronic devices, deposition of a conductive layer on a substrate, such as a copper layer used to fill features formed within a dielectric material, results in excess copper deposited on a face of the substrate and a peripheral edge of the substrate that wraps onto the face. The excess copper on the face can cause problems such as shorts in the circuit. Additionally, the excess copper extending onto the edge of the substrate can lead to delamination of the copper layer and other problems even if the edge portion is part of an unusable section of the substrate. Therefore, the excess copper must be removed from both the edge and the face of the substrate prior to subsequent processing of the substrate, which may include the addition and removal of additional layers of conducting, semiconducting, and dielectric materials in order to form multilevel interconnects of the integrated circuit.
Electrochemical Mechanical Processing (Ecmp) provides one technique used to remove the excess copper from the face of the substrate surface by electrochemical dissolution while concurrently polishing the substrate with reduced mechanical abrasion as compared to conventional Chemical Mechanical Polishing (CMP) processes. Electrochemical dissolution is performed by applying a bias between a cathode and the substrate surface to remove the copper from the substrate surface into a surrounding electrolyte. The bias may be applied to the substrate surface by a conductive contact disposed on or through a polishing material upon which the substrate is processed. The mechanical component of the Ecmp polishing process is provided by a relative motion between the substrate and the polishing material that enhances the removal of the copper from the substrate. Direct contact between the substrate and the polishing material removes a passivation layer protecting the copper, thereby enabling the polishing and planarization via Ecmp.
Conventional CMP effectively only removes the excess copper on the face of the substrate and not the edge of the substrate since the polishing material does not contact the edge of the substrate. Therefore, an edge bead removal (EBR) step is currently required between the deposition step and the conventional CMP process. The EBR may occur within the same system used for deposition and includes the additional time consuming process of spinning the substrate as a nozzle directs an etching solution onto the excess copper along the edge of the substrate. The nozzle for the EBR requires adjustments and tuning in order to attempt to selectively direct the etching solution at only the desired edge portion of the substrate. Thus, the additional EBR step in the IC manufacturing increases costs by slowing throughput, increasing the overall complexity of the system used for deposition, and requiring use of additional consumable material.
Therefore, there exists a need for an improved method and apparatus for removal of a deposited conductive layer along an edge of a substrate.